Quoted:
I think AR performance has modified the cone angle in their SPC II chamber and are calling it 6.8x43.  Small change, keeps the small chance of some copper build up in the chamber from occurring, doesn't change anything else really. Personally I think they should have made the modification under the table, the last thing this poor misinformed round needs is another change.

Quoted:


I agree with the above statement.  AR Performance has done wonderful things for the 6.8 and its followers.......but giving
the round ANOTHER chamber designation was a horrible idea.  To me it is adding more confusion and frustration than ANY
possible improvement.  

By the way, I have purchased the upgraded "Super Bolts" from AR Performance, so please don't consider me a "hater" in
ANY sense of the word.

Chamber discussion
Default 6.8 chambers- SAAMI, SPCII, DMR, 6.8x43, Noveske Mod 1

   There have been lots of threads about this lately for some reason so I'll try to explain it.
   Formal names first, slang after.

   (2004)Remington 6.8x43 SPC-(SAAMI)- has a .050 freebore and when submitted to SAAMI had the correct 45 degree cone angle, has a .278 diameter freebore. Some drawings from PTG has a 80 degree cone angle, no one knows where the error originated.

   (Jan 2006)6.8 Remington SPCII-(SPCII)- had a .100 freebore originally drawn by Art of SSA or Barrett not known for sure had the correct 45 degree cone angle, has a .278 diameter freebore, .3085 neck. Some drawings from PTG has a 80 degree cone angle.

   (2007)6.8x43 DMR (DMR)- has a .095 freebore, .277 dia and a .305 neck diameter it was designed to correct the bad 80 degree cone angle and be a little more accurate in stainless match barrels because of the shorter freebore and .277 dia leade. Only used in ARP stainless match barrels.

   (2008) DMR-C enlarged only enough to take into account the thickness of the chrome in the chamber, neck .0307/.3075-Used only in the chrome lined barrels we had produce in late 2008 and sold in early 2009

   (2009) 6.8x43- has a .095 freebore, .2775 dia with the correct 45 degree cone angle and a .3085/.309 neck. A call came in one day which I missed so they called Tim_W, they said they were planning to submit a new drawing to SAAMI with the help of either Rem or Hornady to get the better spec chamber approved by SAAMI. They said they were planning on submitting the SPCII but wanted our input since we had tested the chambers more than anyone. Tim and I talked about what would be best for a true combat chamber, not a hunting or match chamber.
   We added a very small amount of taper in the neck and body to aid extraction, the freebore was increased to .2775 from what the DMR chamber had, The neck dia was increased to .3085/.309 taper. We guessed if the mil would adopt the cartridge they would call it the 6.8x43 Nato so we just dropped the "Remington" and "SPC" from the name and Tim sent it back to the person that called noting these would be our recommended changes. Of course nothing happened with SAAMI but that is how the 6.8x43 that I presently use came about.

   Noveske mod 1-no real idea, they say it has a .100 freebore.

   (2010) New SPCII- Ben with Bison posted a new SPCII drawing that shows a .114 long freebore with .278 diameter and the correct 45 degree cone angle, everything else is the same as the other SPCII.

   IMO all of these chambers except the original "Remington 6.8x43 SPC"(SAAMI) will handle high performance ammo.

   These chambers seem to confuse many possibly because the public has been exposed to the chambers and given more info than what has been released about the 5.56 and 308 chambers. There are 14 308 chambers that I know about but most of the public thinks there are only 2 the 308 and the 7.62x51 nato. There are at least 10 223/.556 chambers that I know of, the 6.8 isn't different it is just that there is a lot more info being passed around to the public about it.

Quoted:
You'll be hard pressed to find any 6.8 barrel maker using a chamber with the wrong cone angle, I think their was ONE reamer that got put out with an 80* cone angle instead of the proper 45* cone angle but since everyone has started using the correct 45* cone angle so buying a barrel that's wrong in this sense will be almost impossible, it's one of those things some like to mention to make it seem like they are better when it's a non problem to begin with.

The 6.8x43 chamber lead is .005" shorter than the original spec-II chamber lead(.095" vs .100") and a little more than the new spec-II chamber that has the .114" lead that I'm not sure if anyone is even using(WOA/ GTS/ Rainier all uses the original .100" lead) but PTG does make the reamer listed as 6.8 Rem SSA, I think it's used more for comparison than anything to make the SPC-II chambers seem longer than they are and maybe not as accurate when I don't know of anyone using them.

Quoted:
This is my first post here on ARF but im not a total noob.  I have two ars and am looking to diversify my stable so to speak with a 6.8 upper.  I am looking pretty hard at ar performance.  I can't decide between the SPC II chamber Harrison offers and the newer 6.8 x 43.  My question is what if any difference in function/accuracy should be expected from these two different specifications.  I also understand that the newer 6.8x 43 has a slightly different type of rifling.  Sorry for the long winded post I am just on the fence and need some advice.  I would greatly appreciate input from those who have experience with the 6.8 round.  Thanks in advance!

Quoted:

Kind of like Noveske calling his chamber the Mod 1 isn't it? So yet another chamber.
The 6.8x43 chamber has been around for 2 years and was only changed then because the SSA ammo was too large to fit in the other chamber.
The SPCII chamber now has a  .278 diameter .114 long freebore, the 6.8x43 has a .2775 diameter .095 freebore so it isn't a SPCII with the cone angle changed like project irene thinks.
The error of the cone angle was found in 2007, ARPs cone angle has always been different than the SPCII.

Quoted:
here is a quote from Harrison at AR Performance: